(a)[2]
Analysis of a DNA sample showed that $33\%$ of the nitrogenous bases were guanine. Calculate the percentages of the remaining bases in this DNA sample.
(b(i))[1]
Suggest why a larger mass of the mixture is needed compared with a single optical isomer.
(b(ii))[1]
Suggest a problem that could occur when a mixture of optical isomers is taken.
(c(i))[4]
Four structural isomers with the molecular formula $\text{C}_5\text{H}_{10}\text{O}$ are aldehydes. Draw the structures of these aldehydes.
(c(ii))[1]
The NMR spectrum of one of these isomers has four absorptions. Which isomer P, Q, R or S produces this spectrum?
(c(iii))[1]
Predict the number of absorptions that each of the other three isomers would give.